The invention relates to a circuit package for power semiconductor components, and more particularly to a package which provides interconnection design flexibility yet still maintains high heat dissipation capability.
Heat dissipating power conditioning components, such as SCR's, triacs, transistors, MOSFETs, and rectifying bridges, are typically mounted on an electrically insulating thermally conductive substrate, such as rigid ceramic, together with lead frame means and conductive films or the like constituting a hybrid circuit. An electrically insulating housing covers the substrate and the circuit means from above. A heat sink may be clamped to the bottom of the housing to intimately contact the bottom side of the ceramic substrate to dissipate the heat generated by the power conditioning components, all as is well known.
The present invention provides improvements in the lead frame and housing structure. The lead frame structure includes control lead frames for carrying gating signals and the like, and higher capacity power lead frames for carrying the main or rated current. The power lead frames extend from the circuit components on the substrate integrally upwardly beyond the top of the housing and include portions bent laterally across the top external surface of the housing for cooperating with terminal connection means in the top housing wall therebelow. The power lead frames provide a continuous integral electrical connection without intermediate discreet connectors, eliminating additional junctions which otherwise present additional thermal barriers reducing thermal conductivity efficiency.
In one embodiment, the improved lead frame and housing structure is provided in combination with an external printed circuit board extending laterally across the top of the housing. The control lead frames extend integrally upwardly beyond the top of the housing and are connected to the external printed circuit board. The laterally bent external portions of the power lead frames cooperate with attachment means in the top wall of the housing and power terminal portions of the external printed circuit board, and are clamped between the latter two.
The present invention also facilitates internal interconnection of the circuit means on the substrate. The lead frames have portions extending along the substrate, and portions extending normal to the substrate from a given periphery. Connection means are provided for selectively connecting a peripheral lead frame portion on said substrate to a central portion of the circuit means on the substrate within the boundary of the noted periphery and insulatively bypassing designated portions of the circuit means therebetween. A central lead frame has its underside partially etched to a given depth to accomodate a layer of insulation between the central lead frame and printed circuits therebeneath on the substrate. An electrically conductive bridge is jumpered between the central lead frame and a peripheral lead frame portion for passing above a designated power conditioning component in spaced apart relation.